Add trilinos-solvers variant to nalu-wind package. (#35267)

* Add trilinos-solvers variant to nalu-wind package.
   This allows nalu-wind to be built against a trilinos installation
   which doesn't have amesos2, belos, ifpack2, or muelu enabled, if
   the nalu-wind user provides the spec 'nalu-wind@master~trilinos-solvers'
   Support for these solver-packages remains on by default.
* Fixed a style issue reported by CI.
* Incorporate change in wording suggested from review comments.
   ... to clarify that at least one, or both, of hypre and/or
   trilinos-solvers must be enabled. The error condition is if
   both are disabled.
* That style checker is picky...
* It really did want a trailing comma...

var/spack/repos/builtin/packages/nalu-wind/package.py

@@ -42,7 +42,8 @@ class NaluWind(CMakePackage, CudaPackage):
     )
     variant("openfast", default=False, description="Compile with OpenFAST support")
     variant("tioga", default=False, description="Compile with Tioga support")
-    variant("hypre", default=False, description="Compile with Hypre support")
+    variant("hypre", default=True, description="Compile with Hypre support")
+    variant("trilinos-solvers", default=True, description="Compile with Trilinos Solvers support")
     variant("catalyst", default=False, description="Compile with Catalyst support")
     variant("fftw", default=False, description="Compile with FFTW support")
     variant("boost", default=False, description="Enable Boost integration")
@@ -52,7 +53,7 @@ class NaluWind(CMakePackage, CudaPackage):
     depends_on("yaml-cpp@0.5.3:")
     depends_on(
         "trilinos@13:"
-        "+exodus+tpetra+muelu+belos+ifpack2+amesos2+zoltan+stk+boost"
+        "+exodus+tpetra+zoltan+stk+boost"
         "~superlu-dist~superlu+hdf5+shards~hypre+gtest"
     )
     depends_on("trilinos~cuda~wrapper", when="~cuda")
@@ -62,6 +63,11 @@ class NaluWind(CMakePackage, CudaPackage):
     depends_on("openfast@2.6.0: +cxx", when="+openfast")
     depends_on("tioga@master:", when="+tioga")
     depends_on("hypre@2.18.2: ~int64+mpi~superlu-dist", when="+hypre")
+    depends_on("trilinos+muelu+belos+amesos2+ifpack2", when="+trilinos-solvers")
+    conflicts(
+        "~hypre~trilinos-solvers",
+        msg="nalu-wind: Must enable at least one of the linear-solvers: hypre or trilinos-solvers",
+    )
     depends_on("kokkos-nvcc-wrapper", type="build", when="+cuda")
     for _arch in CudaPackage.cuda_arch_values:
         depends_on(
@@ -105,6 +111,7 @@ def cmake_args(self):
         if "+hypre" in spec:
             args.append(self.define("HYPRE_DIR", spec["hypre"].prefix))
 
+        args.append(self.define_from_variant("ENABLE_TRILINOS_SOLVERS", "trilinos-solvers"))
         args.append(self.define_from_variant("ENABLE_PARAVIEW_CATALYST", "catalyst"))
         if "+catalyst" in spec:
             args.append(